A number of chronic infections of the central nervous system are under investigation. Particular emphasis is now being placed on Subacute Sclerosing Panencephalitis, Multiple Sclerosis, Amyotrophic Lateral Sclerosis and Parkinson's disease. A registry of patients with SSPE has been continued. The registry is being maintained to determine the possible affect of measles immunization programs on the course of the epidemiology of SSPE. Tissues from MS, ALS patients are being studied by cocultivation, electron microscopy as well as a variety of techniques for virus isolation. Approach to treatment of SSPE are being pursued and methods for the early diagnosis of MS are being investigated. Cellular immune studies are being extended for patients with MS. Serological tests of CSF from these patient groups will be conducted with a variety of viral antigens.